1. Field of the Invention
The present invention relates to a plate-making type printing press, multi-color printing press and plate-making type printing method for manufacturing printing plates on a printing press, and more particularly relates to a plate-making type printing press, multi-color printing press and plate-making type printing method in which a printing plate is manufactured by writing an image on a plate drum, and printing is performed using this printing plate.
2. Description of the Related Art
In offset printing presses, a manufactured PS plate (a printing plate) is mounted on a printing cylinder, dampening water and ink are supplied to this PS plate, the image on the PS plate formed by the repellent action of the dampening water and ink is transferred onto a blanket cylinder, and this image is printed on paper. However, in this method, in order to alter the content of the printing, it is necessary to perform an operation in which a printing plate.(PS plate) is manufactured by a separately installed plate-making machine, and the printing cylinder or PS plate of the printing press is replaced.
A printing-press type plate-making method in which plate-making is performed on a printing press has been proposed as a means of eliminating this replacement work. For example, in Japanese Patent Application Laid-Open No. H1-152459, a method is proposed in which a printing cylinder is coated with a photosensitive resin, this photosensitive resin is exposed and developed so that a printing plate (printing plate) is formed on the printing cylinder, dampening water and ink are supplied to this printing plate, the image formed on the printing plate by the repellent action of the dampening water and ink is transferred onto a blanket cylinder, and this image is printed on paper. In this method, the printing plate is regenerated by dissolving and removing the photosensitive resin on the printing plate in order to make new plate.
In such an apparatus in which plate-making is performed on a printing press, it is necessary to perform plate-making on the printing cylinder without lowering the printing performance of the printing press; in order to realize an actual apparatus, the following problems must be solved:
First of all, in order to expose the printing cylinder, it is necessary to write an image onto the rotating printing cylinder from a writing device. A writing head is utilized for this writing. If the position of the writing head relative to the printing cylinder is accurate, high-precision writing can be performed, so that a printing plate on which a high-resolution image is written can be formed.
However, in offset printing presses, in order to adjust the paper thickness and printing position on the paper, a mechanism that adjusts the position of the printing cylinder during printing is provided. When such an adjustment is performed, the phase and positional relationship of the writing head and printing cylinder deviate, so that it becomes difficult to manufacture a high-precision printing plate during plate-making.
Secondly, in the case of such a method in which printing plate regeneration is performed on a printing press, a plurality of different types of solutions (e.g., photosensitive resin, developing solution, stripping solution) must be applied to the printing cylinder. Accordingly, in conventional techniques, application devices for various solutions are installed around the printing cylinder. However, when such application devices for various solutions are installed around the printing cylinder, the size of the printing press as a whole is increased, so that it becomes difficult to realize a compact printing press.
Third, in the developing of the printing plate on the printing cylinder, a method is known in which the printing plate is developed by rotating the printing cylinder so that various parts of the printing plate are successively caused to pass through the developing solution inside a developing vessel, thus dissolving the image portions (or non-image portions) of the printing plate on the printing cylinder. This developing process proceeds as a result of a chemical reaction between the developing solution and the printing plate; conventionally, therefore, the progress of the developing process is controlled by controlling the time for which this printing plate passes through the developing solution (i.e., the immersion time), so that the printing plate is appropriately developed.
In this method, however, since the printing plate passes through the developing solution, a certain amount of developing solution must be accommodated inside the developing vessel. As a result, the developing solution tends to be scattered as the printing plate passes through, so that in cases where other units are installed inside the apparatus, these other units are soiled, thus causing a drop in performance. Furthermore, there are restrictions on the positions of such units relative to the printing plate, so that there is little degree of freedom in the layout of the apparatus.
Increasing the size of the developing vessel installed at the lowermost part of the printing plate is an effective means of preventing such scattering of the developing solution inside the developing vessel. However, if the size of the developing vessel is increased, the size of the apparatus that accommodates this developing vessel is also increased.
Specifically, in a printing press that has a plate-making function, it is necessary to install a plate-making mechanism that includes a developing apparatus around the printing cylinder in addition to a dampening water and ink supply apparatus. If the developing apparatus is large, the size of the printing press itself is increased; as a result, it is difficult to realize a small plate-regenerating type printing press.
Fourth, when a photosensitive flat printing plate is formed by coating a printing plate body fastened to a printing cylinder with a photosensitive plate agent from a photosensitive plate agent supplying and coating apparatus, it is necessary to produce a coating layer with good flatness that is free of streaks or spots. Conventionally, in regard to methods used to apply the photosensitive plate agent in the working of plate-making methods on a printing press, all that is known is a description to the effect that a roller coating system, blade system or spray system can be used, as is indicated (for example) in Japanese Patent Application Laid-Open No. H9-99535. In concrete terms, it is not known what type of method or apparatus is suitable.
Fifth, in offset printing presses, it is necessary to open the parts that cover the printing unit in order to expose the printing unit for purposes of internal cleaning, replacement, maintenance and the like. As is described in U.S. Pat. No. 5,630,363, Japanese Patent Application Laid-Open No. H11-314353 and the like, the opening mechanism in a conventional offset printing press is constructed from a mechanism that causes the covering parts to swing across the printing unit.
However, the structural space on the upper side of the printing unit is already occupied by other devices, or else it is necessary to empty this structural space. Accordingly, in most cases, this space cannot be freely used. Furthermore, in the case of application to a printing press that has a plate-making function, access to the printing unit is difficult, and there is interference with the plate-making mechanism; furthermore, the apparatus is complicated.